ODE Simulation

Hi,

How would you simulate the following equation in simulink:

MA = a + b*V + c*V^2 + d*V^3

Where M, a, b, c and d are constants, A = acceleration and V = velocity. I have attached a screenshot of my attempt:

When i replace the constants with numbers I always get a singularity error that the input to my integral is Inf or Nan. Is there something fundamentally wrong with my attepmt or...

Answer 1

[Guy Rouleau]

This looks good at first look. Seth has a nice post on this topic:

http://blogs.mathworks.com/seth/2008/05/23/how-to-draw-odes-in-simulink/

I would guess that your model goes to infinity because you miss a (-) sign. Take the example of a mechanical system, the friction should be in opposite direction of the velocity. If the friction is in the same direction and proportional to the velocity, you will definitely end up accelerating infinitely fast!